Connecting systems and in particular fiber optic connecting systems present significant installation and maintenance problems. Installation techniques include fiber/cable preparation; termination of the fiber in the pin or socket terminus and handling/cleaning of termini during installation in a connector. Termination of the fiber within the terminus must be accomplished by a means which will firmly affix the fiber and which will prevent the fiber from experiencing any movement from the position established. It is known that exposure to broad temperature differentials can cause slight axial displacement or pistoning of the fiber end in the terminus. In prior art it has been shown that by intentionally leaving a slight gap between fibers the danger of pistoning is significantly reduced.
Whatever the means of terminating and firmly confining the fibers in the terminus, the task is delicate because of the importance in dealing with an optical fiber, not to stress it or to produce micro-bending which can result in severe damage to the fiber or substantially reduce the quality of an optical signal being transmitted.
In field termination situations, it is advantageous to utilize methods which require minimum skill, are relatively easy to use and which provide a rugged, durable terminus to protect and align the terminated fiber. One method used in prior art is to terminate with epoxy. Epoxy will firmly hold the fiber in place in the terminus once it is set and cured properly. However, the handling of epoxy in a field application can be troublesome. Mixing the epoxy, applying it and curing it are not easily accomplished tasks, especially in a field setting with possible contamination, confined workspace and lack of time for allowing curing to take place. Accelerated curing can be accomplished with external heat applied, but this may be hazardous with electric arcing in explosive environments or the heat may not be uniformly applied causing improper termination which is not easily detectable.
Another method of terminating a fiber to a connecting terminus is to crimp the fiber into the terminus. Mechanical crimping of the metal terminus body onto the buffered fiber can be safely used to firmly affix the fiber within the terminus. Care must be exercised to assure that the fiber construction includes adequate firm yet resilient buffer coating material to be crimped and that the amount of crimping is precisely controlled to assure that the fiber is firmly held in place and yet the metal crimped terminus body is not inducing excessive stress or microbending when crimped onto the optical fiber.
Yet another aspect of fiber termination in a connectorized fiber optic terminus is the manner of end preparation of the optical signal transmitting fiber itself. Fiber ends must have a mirror-smooth finish perpendicular to the fiber central axis for optimum signal transmission. This end finish can be accomplished through a series of polishing steps. The final polish is a very fine controlled operation attempting to leave the fiber end with the desired high quality mirror endface finish. However, in field situations, using polishing materials, special bushings and somewhat skilled polishing techniques, may be disadvantageous, depending on the field terminating conditions.
An alternative to using polishing for terminating fibers is to use the cleaving method. In cleaving, the fiber is generally placed in tension or bent to the side to provide tension on the periphery of the fiber. A scribing tool with a diamond scriber is brought into passing contact with the fiber periphery, inducing a stress on the fiber. This stress concentration results in a crack initiation and a final crack propagation across the fiber diameter. When properly controlled, the fiber endface created will have a perpendicular or controlled angle mirror-smooth finish.
Because the fiber is made of glass and is subject to damage if the endface comes in contact with foreign objects, it must be protected. Placing the fiber within a terminus body and affixing it in place with crimping or epoxy, and then cleaving the fiber assures that the finished fiber end will be protected by the terminus body from external damage.